1. Field of the Invention
The invention is directed to circular traveling grate machines and, more particularly, it is directed to those circular traveling grate machines which require minimum gas leakage such as horizontally disposed, circular traveling grate retorts.
2. Description of the Prior Art
Circular traveling grate retorts are characterized by distinct processing zones and material charging and discharging zones. Ideally, the processing gas in each of the several processing zones is efficiently isolated from the adjacent zones to prevent gas leakage from one zone into another. It is also beneficial to isolate the supporting components of the individual pallets which make up these grates in order to insure trouble free mechanical performance. Finally it has been a continuing goal in the field of circular traveling grate retorts to provide a pallet capable of quickly and simply discharging the burden thereon after processing has been completed.
U.S. Pat. No. 3,302,936 discloses a circular traveling grate machine in which individual pallets are supported by three wheels, a pair of forward laterally disposed wheels and a single centrally disposed rear wheel. The forward wheels travel along a horizontal trackway and the rear wheel rides on a centrally located rail which drops below the horizontal plane of the trackway in order to dump the pallet. The rear wheel of each pallet travels through the processing zones and is continuously subjected to excessive heat. This results in a short working life for the rear wheel and its supporting components. In an attempt to isolate the supporting components of a pallet, U.S. Pat. No. 2,825,550 discloses a straight traveling grate in which a longitudinal seal is provided between the hood and the windbox to form a tunnel through which the wheels supporting individual pallets travel. The tunnel is provided with flexible transverse closure members which allow the pallet wheels to enter and to exit the tunnel. No consideration is given in this patent to the discharging of materials in a circular grate and the sealing problems which are attendant therewith. It has also been known to utilize false windboxes as transverse seals in traveling grates. Inert gas is injected through such windboxes in order to isolate zones in a retort. Examples of this can be examined in U.S. Pat. Nos. 3,044,756 and 4,193,862.
It is an object of the present invention to provide a circular traveling grate machine which isolates the processing zone from the remainder of the machine and provides an isolated tunnel in fluid communication with the charging and discharging zones of the retort. The support components travel through this tunnel safe from the adverse effects of contact with heated process gases.
It is also an object of this invention to provide a retort which completely encapsulates the process zone therein.
It is still another object of this invention to provide a pallet for movement along a circular trackway, each pallet mating with each immediately preceding and each succeeding pallet to form a continuous grate surface and each pallet capable of independent pivotal movement relative to the other pallets.